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  <title>Document</title>

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<script>
  //    var _instanceof = function(a, b){ // 判断a是否在b的原型链上

//    if (a.__proto__ === b.prototype) return true;// 找到Object.prototype停止

//    if (a.__proto__ === null) return false;

//    // if (a === null) return false; // 应该都是可以的

//    return _instanceof(a.__proto__, b);
// }

// var _instanceof = function(a, b) {
//    let L = a.__proto__;
//    let R = b.prototype;

//    while(true) {
//        if (L === R) {
//            return true;
//        }

//        if (L === null) {
//            return false;
//        }// a.__proto__ === null => a === Object.prototype, 已经找到了原型链的最顶端

//        L = L.__proto__;
//    }
// }
// let a = ["able","age","are"]
// let b=["dog","racecar","car"]
// let c=["national","arrival","mental"]
// const newArr=[]
// function getA(arr){
//   for(i=0;i<arr.length;i++){

//   }
// }
</script>
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